The invention relates to a matrix converter for transforming electrical energy between a voltage source, such as a power supply network, and a current source, such as a motor. The invention is particularly applicable to controlling traction motors in the field of railways.
U.S. patent application Ser. No. 2001/0026427 A1 discloses a matrix converter comprising a 3xc3x973 matrix made up of both-way switches for powering an asynchronous motor from a three-phase network. By means of its modular topology, such a matrix converter offers the advantage of making it possible for a given alternating current (AC) to be converted directly into AC at a different voltage and at a different frequency by appropriately controlling the various switches, unlike the fixed-structure converters that are usually used and which require an AC-to-DC rectifier, a DC-to-DC chopper, and a DC-to-AC uninterruptible power supply (UPS) to be associated in series and to be combined with filter capacitors in order to obtain the same result.
However, in such a matrix converter, the both-way switches are constituted by associating diodes and Integrated Gate Bipolar Transistor (IGBT) components, which suffer from the drawback of not being capable of withstanding high voltages, since the most robust IGBT components that are currently commercially available are limited to an operating voltage of about 6.5 kV. In addition, such an IGBT component suffers from the drawback of having a control gate that must be isolated from its collector and from its emitter, which poses problems when the voltage across the terminals of the IGBT component becomes high.
Therefore, an object of the present invention is to provide a matrix converter of a novel type that can operate at high voltages while remaining very compact. Another object of the invention is to provide a matrix converter in which switch control is naturally isolated from the terminals of said switches.
To this end, the invention provides a matrix converter for transforming electrical energy between at least one voltage source, in particular a power supply network, and at least one current source, in particular a load, said converter including a matrix of switches connecting the voltage sources to the current sources, wherein each of the switches has two terminals disposed in respective distinct parallel planes and a photoconductive diamond substrate interposed between the two terminals of the switch, each switch being controlled by means of a light source irradiating the diamond substrate interposed between the two terminals.
In particular embodiments, the matrix converter of the invention may have one or more of the following characteristics taken in isolation or in any technically feasible combination:
the diamond substrate is obtained by a chemical vapor deposition (CVD) method;
the terminals are formed by metal-plating the diamond substrate by vapor deposition of titanium, platinum, and gold in succession;
the light source is an ultraviolet source;
for each switch, the light source is disposed facing one of the two terminals of the switch, said terminal being provided with at least one opening making it possible for the radiation from said source to pass through to the diamond substrate interposed between the two terminals;
a single diamond substrate is interposed between all of the terminals of the matrix of switches;
each switch of the converter is formed by an individual diamond substrate which is supported by a ceramic substrate, said individual diamond substrate being bonded to the supporting ceramic substrate via a layer of glass; and
each switch has one terminal connected to a voltage source via a conductor track disposed on one face of the ceramic substrate, and one terminal connected to a current source via conductor tracks carried by the opposite face of the ceramic substrate.